‘Katelli’ is a product of a breeding and selection program for outdoor pot mums (garden mums) which had the objective of creating new chrysanthemum cultivars with a decorative type flower, a natural season flower date around September 13-20; blooming for a period of 5 weeks. The new plant of the present invention comprises a new and distinct cultivar of chrysanthemum plant ‘Katelli’ is a seedling resulting from a crossing program, which was set up by a previous breeder, and which records are unknown to the inventor. The new and distinct cultivar was discovered and selected as a flowering plant by Mark Roland Boeder on a cultivated field in Rijsenhout, The Netherlands in 2001. The first act of asexual production of ‘Katelli’ was accomplished when vegetative cuttings were taken from the initial selection in 2001 in a controlled environment in Rijsenhout, The Netherlands, and further propagated at this location. The new cultivar has been found to retain its distinctive characteristics through successive propagations.